Various types of process chambers are available for processing different types of workpieces. The workpieces may comprise, for instance, glass plates, films, ribbons, solar panels, mirrors, liquid crystal displays, semiconductor wafers, and the like. Many different types of process chambers are available, for instance, for processing semiconductor wafers during the manufacture of integrated circuit chips. The process chambers may be used to anneal the wafers, carry out chemical vapor deposition, physical vapor deposition, plasma and chemical etching processes, thermal processes, surface engineering and other processes. These types of process chambers typically contain a workpiece support for holding the workpiece within the chamber.
In many processes, it is desirable to control the temperature of the workpiece during processing. Processes can be optimized, for instance, if the temperature of the workpiece is uniform and is increased and decreased at desired rates and to desired maximums and minimums.
In the past, workpiece supports have been used to heat workpieces, cool workpieces, or to otherwise control the temperature of workpieces. In U.S. Pat. No. 5,609,720, in U.S. Pat. No. 5,761,023, and in Japanese Patent Application Number S63-78975 (1988) having Publication Number H1-251735 which are all incorporated herein by reference, workpiece supports are disclosed having an upper surface that define annular shaped channels filled with heat conducting gas at different pressures which contact the bottom surface of a workpiece for controlling the temperature of the workpiece.
For instance, U.S. Pat. No. 5,761,023 discloses a workpiece support having multiple pressure zones that are provided on the top surface of the support. A sealed area is provided between the two different zones to allow different gas pressures in the two zones. A higher gas pressure is provided to a zone corresponding to an area of the workpiece where greater heat transfer is desired. In this manner, the temperature of the workpiece can be controlled while the workpiece is being exposed to a process wherein the process can affect the temperature of the workpiece.
Although various attempts have been made to design workpiece supports that can control temperature non-uniformities and workpieces held on the workpiece support, various deficiencies and drawbacks still remain. Thus, a need exists for further improvements in workpiece supports capable of controlling the temperature of a workpiece within a process chamber.